Electrical submersible pumps (ESP) are commonly used to pump well fluid from hydrocarbon producing wells. A typical ESP has a centrifugal pump driven by an electrical motor. A pressure equalizer or seal section is usually located between the motor and the pump reduce a pressure difference between lubricant in the motor and the hydrostatic well fluid pressure. The motor drive shaft normally connects to a drive shaft in the seal section, which in turn connects to a pump shaft in the pump. One or more shaft seals at the upper end of the seal section seal against the entry of well fluid into the seal section. A typical shaft seal is a mechanical face seal having a runner that rotates and is biased against a stationary base. Well fluid seeps between the runner and the base to lubricate the interface between the base and runner.
Well fluid leaking into the seal section around the shaft seal can migrate into the lubricant in the motor, which eventually can be very damaging. An ESP may operate for several years in a well, and wear can occur to the shaft seal. Various proposals have been made over many years to inhibit leakage of well fluid into the motor, however, leakage past a shall seal remains a problem.